Solar Power in Alaska

Last week an article about solar farms in Alaska caught my eye:

https://www.bbc.com/future/article/20200219-the-solar-farms-fighting-climate-change-in-alaska

The discussion indicates that despite the obvious shortcomings of solar power generation in a place that receives so little sunshine during the season of peak energy demand, the cost of solar panels has come down enough to make it worthwhile to install solar farms anyway.

The BBC article also states that, "perhaps surprisingly, Alaska is a sunny place", and cites a 2015 piece by Brian Brettschneider to back up this claim.  However, the BBC author unfortunately made an unwarranted jump from daylight to sunshine; while it's true that year-round daylight totals are actually greater in Alaska than points farther south, the total amount of solar energy is nowhere near as great.

https://www.adn.com/science/article/sunniest-day-year-look-why-alaska-has-most-daylight/2015/06/20/

This distinction raises an interesting question, however: do the long daylight hours and relatively clear skies of early summer produce enough solar energy to be competitive with locations in the Lower 48?  To take a quick look at this, I used data from the CRN sites that have been running since 2002 near Fairbanks and since 2010 on the Kenai Peninsula, and I compared total solar energy in May through July to 3 sites in the central and eastern U.S.

First, here's the average rate of solar energy input available at the surface, based on the full period of record at each site (15-17 years except for 9 years at Kenai).  The two Alaska sites receive less energy despite having much longer daylight hours, but the difference is not huge, and this reflects the point of the BBC article - that there's plenty of solar energy to be harnessed in Alaska for part of the year.  Click to enlarge:

The shortfall in total energy despite longer daylight hours is a function of both cloudiness and solar elevation angle.  The chart below illustrates the cloudiness aspect by showing how much of the clear-sky maximum is received at each location.  On the Kenai Peninsula, most summer days are fairly cloudy, and even in the relatively sunny interior, 6 out of 10 days have enough cloud to keep solar radiation at less than 70% of maximum.  In contrast, 6 out of 10 days have more than 70% of maximum in my neck of the woods (Georgia).

So while solar power does have fairly good seasonal potential in Alaska, even the long daylight hours of summer are not enough to make it fully competitive with the rest of the U.S.